Heat coil
Encyclopedia
Heat coils, also known as protectors, bugs or carbons serve as a surge protector
between the telephone exchange
and outside plant
. They are commonly the last point of appearance
for a telephone circuit
before it leaves the office, for example on the outside plant side of the main distribution frame
. On some CLEC circuits there are two heat coils, the extra one being at the point of interface between their circuit and where the ILEC or RBOC receives it. Their primary purpose is to protect central office equipment from surge
s of high voltage.
If a surge comes down the line it will melt the connection between the central office and outside plant sides, as in a fuse
, thereby protecting the equipment. Some heat coils have springs in them, so that when a surge breaks the circuit their tension is released and the plastic cover pops off as a visual indicator that the line is somehow defective.
Surge protector
A surge protector is an appliance designed to protect electrical devices from voltage spikes. A surge protector attempts to limit the voltage supplied to an electric device by either blocking or by shorting to ground any unwanted voltages above a safe threshold...
between the telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
and outside plant
Outside plant
In telecommunication, the term outside plant has the following meanings:*In civilian telecommunications, outside plant refers to all of the physical cabling and supporting infrastructure , and any associated hardware located between a demarcation point in a switching facility and a demarcation...
. They are commonly the last point of appearance
Point of appearance
Point of appearance is a generic term for any point in a telephone/data circuit from which a technician can test or pull stats. Some appearances are virtual, such as a Digital cross connect system computer terminal. Others are physical, like a punch down COSMIC frame where a technician can place a...
for a telephone circuit
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
before it leaves the office, for example on the outside plant side of the main distribution frame
Main distribution frame
In telephony, a main distribution frame is a signal distribution frame for connecting equipment to cables and subscriber carrier equipment . The MDF is a termination point within the local telephone exchange where exchange equipment and terminations of local loops are connected by jumper wires...
. On some CLEC circuits there are two heat coils, the extra one being at the point of interface between their circuit and where the ILEC or RBOC receives it. Their primary purpose is to protect central office equipment from surge
Voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....
s of high voltage.
If a surge comes down the line it will melt the connection between the central office and outside plant sides, as in a fuse
Fuse (electrical)
In electronics and electrical engineering, a fuse is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit...
, thereby protecting the equipment. Some heat coils have springs in them, so that when a surge breaks the circuit their tension is released and the plastic cover pops off as a visual indicator that the line is somehow defective.